SIU School of Medicine

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Department of Internal Medicine

Electrolyte & Acid-Base Disorders

Knowledge

Students should be able to define and describe:

  • pathophysiology of:
    • hypo- and hypervolemia
    • hypo- and hypernatremia
    • hypo- and hyperkalemia
    • hypo- and hypercalcemia
    • simple and mixed acid-based disorders
    • hypo- and hyperphosphatemia
    • hypo- and hyper-magnesemia
    • respiratory acidosis, metabolic acidosis and metabolic alkalosis
  • presenting symptoms and signs of the above disorders
  • the importance of total body water and its distribution
  • the differential diagnosis of hypo- and hypernatremia in the setting of volume depletion, euvolemia and hypervolemia
  • how to distinguish hyponatremia from pseudohyponatremia
  • how to identify spurious hyperkalemia or acidosis-related hyperkalemia
  • risks of too rapid or delayed therapy for hyponatremia
  • the most common causes of:
    • respiratory acidosis
    • respiratory alkalosis
    • metabolic acidosis
    • metabolic alkalosis
  • how to calculate the anion gap and explain its relevance in determining the cause of a metabolic acidosis
  • how to differentiate saline responsive from saline resistant metabolic alkalosis
  • changes in total body water distribution that occur with aging
  • how altered mental status can contribute to electrolyte disorders
  • tests to use in the evaluation of fluid, electrolyte and acid-base disorders
  • indications for obtaining an arterial blood gas
  • the types of fluid preparations to use in the treatment of fluid and electrolyte disorders

Skills

Students should demonstrate specific skills, including:

  • History-Taking Skills: Students should be able to obtain, document, and orally present a medical history, that differentiates among etiologies of disease including:
    • eliciting appropriate information from patients with volume overload, including:
      • recent weight gain
      • edema or ascites
      • symptoms of heart failure
      • dietary sodium intake
      • changes in medications
      • non adherence to recommended treatment
      • intravenous fluid regimens
    • eliciting appropriate information from patients with volume depletion, including:
      • recent weight loss
      • thirst
      • gastrointestinal losses
      • urinary losses
      • oral intake
      • insensible losses
      • intravenous fluid regimens
    • eliciting appropriate information from patients with electrolyte problems, including:
      • use of diuretics and other medications
      • gastrointestinal losses
      • history of relevant medical conditions:
        • heart failure
        • liver disease
        • renal disease
        • pulmonary disease
        • central nervous system disease
        • malignancy
  • Physical Exam Skills: Students should be able to perform a physical exam to establish the diagnosis and severity of disease including:
    • measurement of orthostatic vital signs
    • identify signs of volume overload including:
      • peripheral edema
      • pulmonary edema
      • ascites
    • identify signs of volume depletion including:
      • tachycardia
      • orthostatic hypotension
      • dry mucous membranes
      • poor skin turgor
    • identify signs of sodium disorders including:
      • lethargy
      • weakness
      • encephalopathy
      • delirium
      • seizures
    • identify signs of potassium disorders including:
      • weakness
      • fatigue
      • constipation
      • ileus
      • cramping
      • tetany
      • hypo- or hyperreflexia
    • identify signs of calcium disorders including
      • cramping
      • tetany
      • Chvostek’s and Trousseau’s sign
      • seizures
      • anorexia
      • constipation
      • polyuria
      • hypo- or hyperreflexia
      • stupor
      • coma
  • Differential Diagnosis: Students should be able to generate a prioritized differential diagnosis recognizing specific history and physical exam findings that distinguish between:
    • hypo- and hypervolemia
    • hypo- and hypernatremia
    • hypo- and hyperkalemia
    • hypo- and hypercalcemia
    • hypo- and hyperphosphatemia
    • hypo- and hypermagnesemia
    • respiratory acidosis and alkalosis
    • metabolic acidosis and alkalosis
  • Laboratory Interpretation: Students should be able to recommend when to order diagnostic and laboratory tests and be able to interpret them, both prior to and after initiating treatment.
    Laboratory and diagnostic tests should include, when appropriate:
    • serum osmolality
    • urinary sodium
    • fractional excretion of sodium
    • anion gaps
    • ECG findings in hyper- and hypokalemia
  • Basic and Advanced Procedure Skills: Students should be able to:
    • insert a peripheral intravenous catheter
    • obtain an arterial blood gas
    • assist in the insertion of a central venous catheter

  • Management Skills: Students should be able to develop an appropriate evaluation and treatment plan for patients including:
    • write appropriate fluid orders for the treatment of:
      • hypo- and hypervolemia
      • hypo- and hypernatremia
      • hypo- and hyperkalemia
      • hypo- and hypercalcemia
    • write appropriate orders for replacing:
      • sodium
      • potassium
      • calcium
      • phosphates
      • magnesium
    • write appropriate orders for correcting:
      • hyperkalemia
      • hypercalcemia
      • hyperphosphatemia
      • hypermagnesemia
    • calculate the water deficit that needs to be corrected to treat hypernatremia
    • identify indications for administration of bicarbonate
    • explain to a patient why intravenous fluids are needed
    • access and utilize appropriate information systems and resources to help delineate issues related to fluid, electrolyte and acid-base disorders

Resources

  • "Diuretic Therapy", Brater,D. Craig, M.D., The New England Journal of Medicine, August 6, 1998, Volume 339, Number 6, pages 387 - 395.
  • "Hyponatremia", Adrogue, Horacio J., M.D., Madias, Nicholas E., M.D., The New England Journal of Medicine, May 25, 2000, Volume 342, Number 21, pages 1581 - 1589.
  • "Hypernatremia", Adrogue, Horacio J., M.D., Madias, Nicholas E., M.D., The New England Journal of Medicine, Volume 342 Number 20 1493 - 1500.
  • Clerkship Seminar, “Acid/Base Disorders”, P. Mehta, MD
  • Clerkship Seminar, “Fluids and Electrolytes”, S. Mitra, MD
    Internal Medicine Clerkship Guide, Paauw, et al, Mosby 2003, 382-388, 395-404

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